The present invention relates to a paper feed apparatus for a sheet-fed press, which draws a paper sheet stacked on the paper stack plate of a paper stack table, grips the leading end portion of the paper sheet with a paper convey member, and feeds the paper sheet onto a feeder board to perform printing.
A paper feed apparatus provided to a sheet-fed press has a paper stack table for supporting a paper stack plate on which paper sheets are stacked. A plate-like feeder board is inclinedly supported in front of the paper stack table such that its front portion is lower than its rear portion. A suction port member that can move vertically and back and forward is provided above the stacked paper sheet. A paper feed roller to be rotated by a driving unit and a paper feed roll opposing the upper circumferential surface of the paper feed roller are provided between the paper stack table and the feeder board.
With this arrangement, paper sheets stacked on the paper stack plate on the paper stack table are drawn one by one from the highest one by the suction port member, and the drawn paper sheet is moved forward. The moved paper sheet is gripped by the paper feed roller and the paper feed roll at its leading end portion, and is fed onto the feeder board as the paper feed roller and the paper feed roll are rotated.
According to the conventional paper feed apparatus having the above arrangement, however, paper sheets are continuously fed onto the feeder board by inserting a paper sheet under a previously fed paper sheet with a slight shift in the feed direction. Therefore, the trailing end portion of the paper sheet which is exposed from the trailing end portion of the previously fed paper sheet must be drawn by the suction port member. Then, when the paper sheet is to be drawn, the paper sheet portion except for the trailing end portion is not held, resulting in an unstable paper feed operation.
For example, Japanese Patent Publication No. 45-12928 discloses an arrangement in which the leading end portion of a paper sheet is drawn by a suction port member. This arrangement will be described. More specifically, this paper feed apparatus has a feed roller, a guide arm, a suction port member, and a guide plate. The feed roller is axially supported above the leading end portion of the stacked paper sheet and rotated by a motor. The guide arm is supported by a link mechanism and moved forward and backward in the horizontal direction so as to enter from the front side to bring the roll at its distal end portion into contact with the lower circumferential surface of the feed roller and to be retreated forward from the entered state. The suction port member is supported by the link mechanism and moved in the vertical direction with respect to the leading end face of the paper sheet to draw the paper sheet. The guide plate is supported above the reciprocal path of the guide arm. A paper feed roller and a paper feed roll that oppose each other in the vertical direction, and a feeder board, three of which are similar to those described above, are provided in front of the guide plate.
With this arrangement, when a paper feed operation is to be performed, first, the suction port member is moved downward from the upper stop position, draws the leading end portion of the paper sheet, and is then moved upward to the upper stop position, and releases the paper sheet. Simultaneously, the guide arm enters below the feed roller, and the roll at the distal end portion of the guide arm is brought into contact with the lower circumferential surface of the feed roller. The released paper sheet is clamped by the feed roller and the roll. When the feed roller and the roll are rotated, the clamped paper sheet is fed forward on the guide plate, gripped by the paper feed roller and the paper feed roll, and fed onto the feeder board.
According to the conventional paper feed apparatus having the above arrangement, as described above, when the suction port member that has drawn the paper sheet is moved upward and releases the paper sheet, the paper sheet is fed to a portion below the suction port member by the rotation of the feed roller and the roll. At this time, after the paper sheet drawing by the suction port member is released, it is quickly moved in the paper convey direction from the stop state. Then, the paper sheet which is being quickly moved forward and the suction port member may undesirably interfere with each other. It is, however, difficult to set the timing so as not to cause this interference. Hence, high-speed printing cannot be achieved. Furthermore, it is difficult to move all the feed rollers and the rolls simultaneously and to cause them to grip the paper sheet at the same contact pressure. Therefore, a paper feed error such as erroneous paper direction tends to occur to increase waste paper.